ON THE EXISTENCE OF NON-MICROBIOTHERIAN AUSTRALIDELPHIAN MARSUPIALS (DIPROTODONTIA) IN THE EOCENE OF PATAGONIA

LORENTE, M.; CHORNOGUBSKY, L.; GOIN, F. J.

PALAEONTOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2016 vol. 59 p. 533 - 547

0031-0239

A diverse assemblage of extinct mammals ofearly?middle Eocene age (Ypresian?Lutetian boundary)come from the Patagonian localities of La Barda andLaguna Frıa around Paso del Sapo in northwestern ChubutProvince (Argentina). Metatherians are well represented,mostly by dental remains of ?Didelphimorphia?, Paucituberculata,Sparassodonta, Microbiotheria, and Polydolopimorphia.Here we analyse three calcanea and one astragalusreferable to the same, indeterminate taxon, from La Barda,showing the fusion of their ectal and sustentacular facets.This facet arrangement characterizes the Australidelphia, amarsupial clade represented by Microbiotheria from SouthAmerica and Antarctica, plus all Australasian lineages.Other australidelphian features shown by these tarsalsinclude: in the calcanea, a reduced peroneal process and atripartite cuboid facet; in the astragalus, a round, very smallastragalar head in relation to the body; a convex trochleawith a half for the tibia and half, in slightly lower position,for the fibula. Their size and other anatomical features suggestthat the new tarsals cannot be referred to the Microbiotheria.Phylogenetic analysis suggests that the La Bardataxon lies within the Australidelphia, and that it is eitherclosely related or belongs to, the Diprotodontia. The existenceof advanced australidelphians in Patagonia adds furtherevidence of the close relationship between Patagonia,Antarctica, and Australia during the Late Cretaceous ? earlyPalaeogene.